The soil is the largest carbon (C) pool in the terrestrial ecosystem, and soil organic carbon (SOC) stocks play an important role in global C dynamics. Alpine grasslands of the Andes are ...characterized by high SOC stocks. Quantifying SOC stocks and unraveling key factors controlling SOC stocks, is necessary to obtain a better understanding of the dynamics of the large C stocks in this environment. However, most studies on C dynamics of the Andes focus on volcanic-ash soils, whereas information about non-volcanic ash soils in this region is scarce. Our objectives were: (i) to estimate SOC stocks in an alpine grassland of the Peruvian Andes (7° 11′S, 78° 35′W) with parent materials other than volcanic ash, and (ii) to identify the underlying soil formation and environmental (SFE) factors and soil properties explaining observed patterns of SOC stocks. We sampled 69 plots up to the parent material to measure soil properties and to calculate SOC stocks, in relation to lithology, land use, grazing intensity, slope angle, slope position and altitude. We applied linear models to identify key factors controlling SOC stocks. Our results showed that total SOC stocks had a mean value of 215 ± 21 T ha−1, whereas SOC stocks of the upper 10 cm and 40 cm comprised 29.3% and 80.0% of total SOC stocks respectively. The variation of the total SOC stocks was mainly explained by soil depth and soil moisture. When soil depth and soil moisture were controlled as conditional variables, lithology became the key factor controlling the total SOC stocks. For the SOC stocks of the upper 10 cm, soil moisture explained a large part of the variation, whereas lithology, grazing intensity and altitude were also significant predictors. Our results also show that when soils are sampled with limited depths instead of the entire soil profile, SOC stocks can be underestimated, and the effects of the SFE factors on SOC stocks can be overestimated.
•The study area had a high level of soil organic carbon stocks (215 ± 21 T ha−1).•Total SOC stocks were largely controlled by soil depth and soil moisture.•Lithology became a key predictor when soil depth and moisture were controlled.•SOC stocks were underestimated without the entire soil profile involved.•Effects of environmental factors were overestimated without the entire profile.
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•Mineralogical composition of proglacial tills is related to source area lithology.•Proglacial tills may act as reservoirs for precipitation.•Effects of proglacial tills on water ...quality are related to till composition.•These effects on water quality do not propagate strongly downstream.
The Río Santa (Ancash, Peru) and its tributaries are an essential source of drinking and irrigation water. Its discharge relies on glacial meltwater, which is diminishing due to the rapid decrease in glacial extent. As a secondary effect, water quality can be compromised (e.g. pH < 3 and high concentrations of SO42− and trace metals). Although this has previously been attributed to pyrite rich Chicama bedrock exposed by glacial retreat, little is known about the occurrence of Chicama fragments in Quaternary glacial sediments and its influence on water quality. This research aims at elucidating this effect by relating observed changes in water quality in streams to presence and chemical composition of morainic ridges in the Quebrada Ulta in the Río Santa basin. Changes in water quality before and after contact with a morainic ridge were assessed using carbonate alkalinity titration, ion analysis and elemental analysis. Moreover, relative contributions of glacial meltwater and precipitation were assessed qualitatively using stable water isotope analysis. We used a novel method to explain the provenance of contaminated glacial sediments using a reconstruction of their source area. The mineralogical composition of a morainic ridge was strongly related to the geology of the source area indicating that mineralogical composition of tills may be predicted using this technique. Effects of glacial sediments in morainic ridges on water quality were minimal but depended on their mineralogical composition. Morainic ridges with a high content of Chicama shales tended to increase solute loads of Mg and SO42−. Additionally, isotope signatures suggest that during the dry season, moraines may act as reservoirs for precipitation-derived shallow groundwater. Clear trends in water quality were observed along the whole flow path of the Río Buín, which could potentially be explained by increased groundwater contribution downstream and shifts in dominant weathering mechanisms. Future research should focus on disentangling these various drivers of water quality in glacial catchments.
The effect of land abandonment as a result of changing land-use policies is becoming more and more important throughout Europe. In this case study, the role of vegetation succession and landslide ...activity on steep abandoned slopes was investigated. The influence of vegetation succession on soil properties over time, as well as how developing root systems affect soil reinforcement was determined. The study was carried out in the Alcoy basin in SE Spain, where the marl substratum is prone to landsliding along steep ravines. The bench-terraced slopes have been abandoned progressively over the last 50 years and show various stages of revegetation. The study was carried out at two scales; at the catchment scale long-term evolution of land-use, vegetation succession and slope failure processes were investigated. At a more detailed scale, vegetation cover, soil properties and rooting effects on soil strength were determined. Results showed that the soil has changed over a period of 50 years with respect to soil properties, vegetation cover and rooting, which is reflected in the activity of geomorphological processes. Vegetation succession progressively limits surface processes (sheet wash and concentrated overland flow) over time, whereas slopes affected by mass wasting processes increase in number. The spatial heterogeneity of infiltration increases over time, leading to increased macro-pore flow towards the regolith zone, enhancing the potential risk of fast wetting of the regolith directly above the potential plane of failure, as was concluded from rainfall simulations. In situ experiments to determine soil shear strength in relation to rooting indicated that roots contributed to soil strength, but only in the upper 0.4 m of the soil. Most failures however, occur at greater depths (1.0–1.2 m) as anchorage by deeper roots was not effective or absent. The observed initial increase in mass wasting processes after land abandonment can therefore be explained in two ways: (1) the limited contribution of anchorage by root systems at potential slip planes which cannot counterbalance the initial decline of the terrace walls, and (2) the fast transfer of rainfall to the potential slip plane by macro-pores enhancing mass movements. However, after approximately 40 years of abandonment, mass wasting processes decline.
A better process understanding of how water erosion influences the redistribution of soil organic carbon (SOC) is sorely needed to unravel the role of soil erosion for the carbon (C) budget from ...local to global scales. The main objective of this study was to determine SOC redistribution and the complete C budget of a loess soil affected by water erosion. We measured fluxes of SOC, dissolved organic C (DOC) and CO.sub.2 in a pseudo-replicated rainfall-simulation experiment. We characterized different C fractions in soils and redistributed sediments using density fractionation and determined C enrichment ratios (CER) in the transported sediments. Erosion, transport and subsequent deposition resulted in significantly higher CER of the sediments exported ranging between 1.3 and 4.0. In the exported sediments, C contents (mg per g soil) of particulate organic C (POC, C not bound to soil minerals) and mineral-associated organic C (MOC) were both significantly higher than those of non-eroded soils indicating that water erosion resulted in losses of C-enriched material both in forms of POC and MOC. The averaged SOC fluxes as particles (4.7 g C m.sup.-2 yr.sup.-1) were 18 times larger than DOC fluxes. Cumulative emission of soil CO.sub.2 slightly decreased at the erosion zone while increased by 56% and 27% at the transport and depositional zone, respectively, in comparison to non-eroded soil. Overall, CO.sub.2 emission is the predominant form of C loss contributing to about 90.5% of total erosion-induced C losses in our 4-month experiment, which were equal to 18 g C m.sup.-2 . Nevertheless, only 1.5% of the total redistributed C was mineralized to CO.sub.2 indicating a large stabilization after deposition. Our study also underlines the importance of C losses by particles and as DOC for understanding the effects of water erosion on the C balance at the interface of terrestrial and aquatic ecosystems.
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DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Farmland abandonment is one of the major land use changes occurring in many rural territories, especially in mountainous regions. Without intervention (passive land management), farmland abandonment ...leads to an expansion of shrubs and forest on formerly cultivated hillslopes and grazing areas. All these land use changes affect the hydrological and geomorphological dynamics of slopes and channels, having important implications for water resources and soil conservation. However, the heterogeneity of abandoned scenarios complicates the assessment of farmland abandonment on water resources and soil conservation. In this Special Issue, we will publish papers that examine the hydrological and geomorphological consequences of farmland abandonment in one (or several) of these abandoned scenarios. Our final purpose is to help water and land managers to select the most sustainable strategy (in terms of water resources and soil conservation) for the land management of marginal rural areas.
Las terrazas agrícolas o bancales constituyen un elemento esencial de la montaña mediterránea europea. Su construcción y mantenimiento exige mucha energía, dando lugar a culturas basadas en el ...aprovechamiento cuidadoso y complejo de las laderas. Hoy laderas enteras de bancales se han abandonado y sufren procesos muy intensos de erosión y revegetación, amenazando con arruinar paisajes culturales de gran valor.En el Valle de Bestué (Pirineo central aragonés) se configuró uno de los mejores paisajes de bancales del Pirineo central. Los bancales alcanzaron el 13,1% de la superficie del valle. Se construyeron para el cultivo de cereales y, con ello, poder alimentar a la población local. Se cultivaron hasta los años cincuenta-setenta del pasado siglo y después se aprovecharon como prados de siega. Desde la última década del siglo XX se abandonaron. El cese del cultivo y la ausencia de pastoreo han cubierto de bosques los bancales en muy pocas décadas; el bosque ocupaba el 13,7% del territorio en 1956 y el 48,7% en 2015. Entre las mismas fechas el paisaje ha perdido heterogeneidad y valor cultural. No obstante, aún se mantienen algunos retazos del paisaje de bancales que deberían conservarse, ya que constituyen un compendio del aprovechamiento agrícola de la pendiente y de conservación del suelo.
This book is designed to assist the civil and geotechnical engineer, geomorphologist, forester, landscape architect or ecologist in choosing ecotechnological solutions for slopes that are prone to a ...variety of mass movements e.g. shallow failure or erosion. Within this book, the ‘engineer’ is used in the global sense to encompass all planners, designers, etc. who are involved in the stabilisation of slopes. We review the types of problematic slopes that may occur and describe briefly the nature of mass movements and the causes of these movements. In this book, we focus on the use of vegetation to stabilize soil on slopes prone to mass movements. Before a plant can be chosen for a particular function, its physical and hydrological properties must be determined, thus the root architecture of grasses, shrubs and trees are described and the soil hydrological and mechanical factors which influence vegetation are discussed. Depending on the use of the slope, the engineer may wish to ascertain either the stability of the slope or the mechanical stability of the vegetation or both, therefore slope stability analysis methods are reviewed and the contribution the vegetation has to the stability of the slope are explained. Models to assess the mechanical stability of vegetation are reviewed. This book also introduces new ecotechnological methods for stabilising active rockfalls on steep slopes and slopes that are prone to soil erosion following wild fires, as well as providing user friendly information on traditional ground bio-engineering techniques and tables of plants suitable for different functions. Case studies where ground bio- and eco-engineering measures have been put into practice are also discussed.
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